Azarsa Ehsan, Jeyhani Morteza, Ibrahim Amro, Tsai Scott S H, Papini Marcello
Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada.
Biomicrofluidics. 2020 Jul 8;14(4):044103. doi: 10.1063/5.0009443. eCollection 2020 Jul.
Microfluidic lab-on-a-chip devices are usually fabricated using replica molding, with poly(dimethylsiloxane) (PDMS) casting on a mold. Most common techniques used to fabricate microfluidic molds, such as photolithography and soft lithography, require costly facilities such as a cleanroom, and complicated steps, especially for the fabrication of three-dimensional (3D) features. For example, an often-desired 3D microchannel feature consists of intersecting channels with depth variations. This type of 3D flow focusing geometry has applications in flow cytometry and droplet generation. Various manufacturing techniques have recently been developed for the rapid fabrication of such 3D microfluidic features. In this paper, we describe a new method of mold fabrication that utilizes water jet cutting technology to fabricate free-standing structures on mild steel sheets to make a mold for PDMS casting. As a proof-of-concept, we use this fabrication technique to make a PDMS chip that has a 3D flow focusing junction, an inlet for the sample fluid, two inlets for the sheath fluid, and an outlet. The flow focusing junction is patterned into the PDMS slab with an abrupt, nearly stepwise change to the depth of the microchannel junction. We use confocal microscopy to visualize the 3D flow focusing of a sample flow using this geometry, and we also use the same geometry to generate water-in-oil droplets. This alternative approach to create microfluidic molds is versatile and may find utility in reducing the cost and complexity involved in fabricating 3D features in microfluidic devices.
微流控芯片实验室设备通常采用复制成型法制造，即将聚二甲基硅氧烷（PDMS）浇铸在模具上。用于制造微流控模具的最常见技术，如光刻和软光刻，需要洁净室等昂贵的设施以及复杂的步骤，特别是对于三维（3D）特征的制造。例如，一种常被需要的3D微通道特征由具有深度变化的相交通道组成。这种类型的3D流动聚焦几何结构在流式细胞术和液滴生成中有应用。最近已经开发出各种制造技术来快速制造这种3D微流控特征。在本文中，我们描述了一种新的模具制造方法，该方法利用水射流切割技术在低碳钢板上制造独立结构，以制作用于PDMS浇铸的模具。作为概念验证，我们使用这种制造技术制作了一个PDMS芯片，该芯片具有一个3D流动聚焦结、一个样品流体入口、两个鞘液入口和一个出口。流动聚焦结被图案化到PDMS平板中，微通道结的深度有突然的、近乎阶梯式的变化。我们使用共聚焦显微镜来可视化使用这种几何结构的样品流的3D流动聚焦，并且我们还使用相同的几何结构来生成油包水液滴。这种制造微流控模具的替代方法具有通用性，可能在降低制造微流控设备中3D特征所涉及的成本和复杂性方面找到用途。
